1. Field of the Invention
The present invention relates generally to semiconductor devices and methods of producing the same and semiconductor chips and methods of producing the same, and more particularly to a semiconductor device having a chip size package (CSP) structure, in which a sealing resin is formed on a semiconductor chip, and a method of producing the same, and a semiconductor chip for such a semiconductor device and a method of producing the same.
Recently, attempts have been made to produce a smaller size semiconductor device having a higher density in order to meet a demand for a smaller electronic device and apparatus. Therefore, a semiconductor device having a so-called CSP structure is employed, the semiconductor device being downsized by being shaped as close to a semiconductor chip as possible.
In order to obtain a package of a real chip size and to increase a production efficiency, so-called wafer level packaging is proposed. According to the wafer level packaging, a substrate is packaged with a plurality of semiconductor chips formed thereon, and the as-packaged substrate is divided into individual small-size semiconductor devices.
2. Description of the Related Art
FIG. 1 shows a semiconductor device 1A obtained by conventional wafer level packaging. The semiconductor device 1A is a semiconductor device of a so-called CSP type and includes a semiconductor chip 2A, a sealing resin 5A and solder balls 4. The semiconductor chip 2A has a plurality of external terminals 3 formed protrusively on its upper surface. The sealing resin 5A is formed on the upper surface of the semiconductor chip 2A so that the upper portions of the external terminals appear partially from the sealing resin 5A. The solder balls 4 are formed on the portions of the external terminals 5A appearing from the sealing resin 5A.
When heat is applied to the semiconductor chip 2A and the sealing resin 5A, which have different expansion coefficients, the sealing resin 5A may come off the semiconductor chip 2A because of a difference in thermal expansion therebetween. In order to prevent the sealing resin 5A from coming off the semiconductor chip 2A, the peripheral portion of the semiconductor chip 2A is formed into a rectangular step-like portion 6 having an L-shaped cross section. According to this structure, the step-like portion 6 is filled with the sealing resin 5A when the sealing resin 5A is formed, so that the sealing resin 5A in the step-like portion 6 produces an anchoring effect. This increases the bonding strength of the sealing resin 5A and the semiconductor chip 2A so as to prevent the sealing resin 5A from coming off the semiconductor chip 2A.
FIGS. 2A through 2G are diagrams for illustrating the outline of the production method of the semiconductor device 1A having the above-described structure. According to FIGS. 2A through 2G, especially, a method of forming the step-like portion 6 is mainly shown. In the production of the semiconductor device 1A, a method of simultaneously obtaining a plurality of semiconductor devices from one semiconductor substrate (hereinafter, a wafer) is taken. A more specific description of the method will be given in the following. First, the circuits of the individual semiconductor chips 2A are formed on the surface (hereinafter, a circuit-containing surface) of the wafer 10. Then, the external terminals 3 are formed on the circuit-containing surface, and a resin film of polyimide or the like (not shown) is formed on the circuit-containing surface for the protection thereof.
Next, as shown in FIGS. 2A through 2C, rectangular grooves 12 are formed in the wafer 10 along predetermined dicing lines (cutting lines) on the circuit-containing surface thereof by employing a dicing saw for grooving (hereinafter, a grooving dicing saw) 11A. After the rectangular grooves 12 are formed, the sealing resin 5A is formed on the same surface on which the rectangular grooves 12 are formed as shown in FIG. 2D. At this point, the rectangular grooves 12 are filled with the sealing resin 5A. Further, the sealing resin 5A is formed so that the upper portions of the protrusion electrodes appear partially from the sealing resin 5A.
Next, as shown in FIGS. 2E and 2F, a dicing process is performed on the wafer 10 using a dicing saw for cutting (hereinafter, a cutting dicing saw) 13. The thickness of the cutting edge of the cutting dicing saw 13 is narrower than that of the grooving dicing saw 11A.
Therefore, as shown in FIG. 2G, each individual semiconductor device 1A obtained after the dicing process includes the step-like portion 6, which is formed as a result of cutting into two each of the rectangular grooves 12 filled with the sealing resin 5A. Since the rectangular grooves 12 are filled with the sealing resin 5A as previously described, the step-like portions 6 formed after the dicing process are also filled with the sealing resin 5A. Therefore, the sealing resin 5A produces the above-described anchoring effect in each of the step-like portions 6 so as to be prevented from coming off each of the semiconductor chips 2A.
FIG. 3 shows a semiconductor device 1B having another structure obtained by the conventional wafer level packaging. FIGS. 4A through 4G are diagrams showing the outline of the production method of the semiconductor device 1B. In FIGS. 3 through 4G, the same elements as those of previously-described FIGS. 1 through 2G are referred to by the same numerals and a description thereof will be omitted.
The semiconductor device 1B shown in FIG. 3 is also a semiconductor device of the CSP type, and has the same basic structure as the semiconductor device 1A shown in FIG. 1. However, according to the semiconductor device 1A shown in FIG. 1, the semiconductor chip 2A includes the step-like portion 6 filled with the sealing resin 5A so that the semiconductor chip 2A and the sealing resin 5A are bonded strongly by the anchoring effect produced by the sealing resin 5A.
On the other hand, according to the semiconductor device 1B shown in FIG. 3, the peripheral portion of the semiconductor chip 2A is formed into a tapered portion 7 covered with the sealing resin 5A. Also according to this structure, an area in which the sealing resin 5A and the semiconductor chip 2A are bonded is increased so as to increase the bonding strength thereof. Therefore, the sealing resin 5A is prevented from coming off the semiconductor chip 2A.
In order to produce the semiconductor device 1B having the above-described tapered portion 7, a grooving dicing saw 11B is employed. The cross section of the edge portion of the grooving dicing saw 11B has a triangular shape as shown in FIGS. 4A through 4C. Triangular grooves 14 are formed in the wafer 10 along predetermined dicing lines (cutting lines) on the circuit-containing surface thereof by employing the grooving dicing saw 11B. After the triangular grooves 14 are formed, the sealing resin 5A is formed as shown in FIG. 4D, so that the triangular grooves 14 are filled with the sealing resin 5A.
Next, as shown in FIGS. 4E and 4F, the dicing process is performed on the wafer 10 using the cutting dicing saw 13. The thickness of the cutting edge of the cutting dicing saw 13 is narrower than that of the grooving dicing saw 11B. Therefore, as shown in FIG. 4G, each individual semiconductor device 1B obtained after the dicing process includes the tapered portion 7, which is formed as a result of cutting into two each of the triangular grooves 14 filled with the sealing resin 5A.
Since the triangular grooves 14 are filled with the sealing resin 5A as previously described, the tapered portions 7 formed after the dicing process are also filled with the sealing resin 5A. Therefore, the sealing resin 5A produces the above-described anchoring effect in each of the tapered portions 7 so as to prevent the sealing resin 5A from coming off each of the semiconductor chips 2A.
The description has been given, with reference to FIGS. 1 through 4G, of the semiconductor devices 1A and 1B of the CSP type and the production methods thereof. On the other hand, there is a semiconductor device including a semiconductor chip obtained by cutting a wafer in advance into individual semiconductor chips.
FIGS. 5A and 5B illustrate the dicing process of a method of producing a semiconductor chip to be included in a semiconductor device of such a type. Dicing is performed along predetermined dicing lines (cutting lines) on the circuit-containing surface of the wafer 10 by employing the cutting dicing saw 13 shown in FIG. 5A, so that individual semiconductor chips 2B are obtained as shown in FIG. 5B.
A thin film formed on top of the wafer 10 in FIGS. 5A and 5B is a contaminant 18. Residues left in the processes performed during the formation of the electronic circuits of the respective semiconductor chips 2B on the wafer 10, such as an impurity diffusion process, a thin film deposition process and a photolithography process, and the residue of the resin film for the protection of the circuit-containing surface of the wafer 10 remain to form the contaminant 18 on the wafer 10. Although not graphically represented, the contaminant 18 exists also on the wafer 10 shown in FIGS. 2A through 2G and 4A through 4G.
FIGS. 6 through 8 are diagrams respectively showing semiconductor devices 1C through 1E each including the semiconductor chip 2B produced by the above-described method.
The semiconductor device 1C shown in FIG. 6 is a semiconductor device of a tape carrier package (TCP) type. The semiconductor device 1C includes the semiconductor chip 2B including bumps 23 formed thereon and a tape automated bonding (TAB) tape 20 including a base film 21 and interconnection lines 22 formed thereon. The semiconductor chip 2B is bonded to the interconnection lines 22 by flip chip bonding. A sealing resin 5B is formed in the area surrounding the junctions of the semiconductor chip 2B and the TAB tape 20 so as to protect the joining points of the bumps 23 and the interconnection lines 22 and a surface of the semiconductor chip 2B on which surface the electronic circuit is formed. Hereinafter, the surface is referred to as a circuit-containing surface of the semiconductor chip 2B.
The semiconductor device 1D shown in FIG. 7 is a semiconductor device of a ball grid array (BGA) type. The semiconductor device 1D includes the semiconductor chip 2B including the bumps 23 formed thereon and a printed-circuit board 24A including the solder balls 4 formed on the lower side thereof. The semiconductor chip 2B is bonded to the printed-circuit board 24A in a face-down manner. The solder balls 4 and the bumps 23 are electrically connected via through holes formed in the printed-circuit board 24A. A sealing resin 5C referred to as an underfill resin is interposed between the semiconductor chip 2B and the printed-circuit board 24A.
The semiconductor device 1E shown in FIG. 8 is a semiconductor device of a face-down ball grid array (FDBGA) type. According to the semiconductor device 1E, which is frequently used for the production of DRAMs, a pad 26 is formed in the center of the circuit-containing surface of the semiconductor chip 2B. A printed-circuit board 24B having an opening in the center portion thereof is provided to face the circuit-containing surface of the semiconductor chip 2B. The printed-circuit board 24B and the pad 26 are electrically connected by a wire 25 provided through the opening.
The solder balls 4 are formed on the lower surface of the printed-circuit board 24B so as to be electrically connected to the pad 26 of the semiconductor chip 2B. Further, a sealing resin 5D is formed between the semiconductor chip 2B and the printed-circuit board 24B and on the sides of the semiconductor chip 2B.
According to the conventional semiconductor devices 1A or 1B, as previously described, the step-like portion 6 or the tapered portion 7 is formed to increase the bonding strength of the sealing resin 5A and the semiconductor chip 2A so as to prevent the sealing resin 5A from coming off the semiconductor chip 2A.
Therefore, according to the conventional production method, the rectangular grooves 12 or the triangular grooves 14 are formed in the wafer 10 along the dicing lines on the circuit-containing surface thereof so as to form the step-like portion 6 or the tapered portion 7. The rectangular grooves 12 or the triangular grooves 14 are formed by employing the grooving dicing saw 11A or 11B as shown in FIGS. 2A through 2C or 4A through 4C. In other words, conventionally, the step-like portion 6 or the tapered portion 7 is formed by machining.
However, forming the step-like portion 6 or the tapered portion 7 by machining inevitably generates residual stress in the position where the step-like portion 6 or the tapered portion 7 is formed. Therefore, when heat is applied to the semiconductor device 1A or 1B, causing a difference in thermal expansion between the semiconductor chip 2A and the sealing resin 5A, a force resulting from the difference in thermal expansion greatly affects the position where the residual stress exists, so that a crack 16 or a breakage 17 is produced in the position where the step-like portion 6 or the tapered portion 7 is formed, as shown in FIGS. 9A and 9B or 10A and 10B.
Further, when the rectangular grooves 12 or the triangular grooves 14 are formed by machining in the wafer 10 by employing the grooving dicing saw 11A or 11B, stress concentration is focused on the corner portions of the rectangular grooves 12 or the bottom portions of the triangular grooves 14, so that the wafer 10 has the crack 16 or the breakage 17 as shown in FIG. 11A or 11B.
Furthermore, a film of the contaminant 18 is inevitably formed on the circuit-containing surface of the wafer 10 through the processes performed during the formation of the electronic circuits of the respective semiconductor chips 2B on the wafer 10. The contaminant 18 has a poor connectivity with each of the sealing resins 5A through 5D. Therefore, if each of the semiconductor devices 1A through 1E is produced using either the semiconductor chip 2A or 2B each including the contaminant 18 remaining thereon, a space 19 is formed between each of the sealing resin 5A through 5D and the semiconductor chip 2A or 2B as shown in FIGS. 9A through 10B or 6 through 8, thus decreasing the reliability of each of the semiconductor devices 1A through 1E.
Further, when the wafer 10 is cut into the individual semiconductor chips 2B simply by employing the cutting dicing saw 13 in the dicing process as shown in FIGS. 5A and 5B, the semiconductor chip 2B has residual stresses generated also in the positions on which dicing is provided because the dicing process employing the cutting dicing saw 13 is also a mechanical operation. Therefore, when the semiconductor chip 2B including the residual stresses is used for the semiconductor devices 1C through 1E, the semiconductor chip 2B may have the crack 16 (or a breakage) as shown in FIGS. 6 through 8 as a result of a difference in thermal expansion between the semiconductor chip 2B and each of the sealing resins 5B through 5D caused by heat application.
It is a general object of the present invention to provide a semiconductor device and a method of producing the same and a semiconductor chip and a method of producing the same in which the above disadvantages are eliminated.
A more specific object of the present invention is to provide a semiconductor device prevented from having a crack or breakage and thus to have increased reliability and a method of producing the same, and a semiconductor chip suitable for such a semiconductor device and a method of producing the same.
The above objects of the present invention are achieved by a semiconductor device including a semiconductor chip including external terminals formed on a surface thereof and a sealing resin formed on the surface of the semiconductor chip, wherein a contaminant film formed on the surface of the semiconductor chip has a laser-processed edge so that a peripheral portion of the surface of said semiconductor chip is bonded to the sealing resin.
According to the above-described semiconductor device, the peripheral portion of the contaminant film is removed by a laser beam projection so that an exposed portion is formed on the peripheral portion of the surface of the semiconductor chip.
When the contaminant film remains on the surface of the semiconductor chip, the bonding strength of the semiconductor chip and the sealing resin is reduced. Therefore, by forming the exposed portion in which the semiconductor chip is exposed, the bonding strength of the semiconductor chip and the sealing resin is increased in the exposed portion so that the sealing resin is prevented from coming off the semiconductor chip.
Further, since the contaminant film is removed by the laser processing according to this semiconductor device, stress generated in the semiconductor chip when the exposed portion is formed can be reduced compared with a semiconductor device formed by a method employing a mechanical operation to remove the contaminant. Therefore, even if force resulting from a difference in thermal expansion between the sealing resin and the semiconductor chip is applied to the exposed portion, the position where the exposed portion is formed is prevented from having a crack or breakage.
The above objects of the present invention are also achieved by a method of producing a semiconductor device, which method includes the steps of (a) removing a portion of a contaminant film from a surface of a semiconductor substrate by a laser beam projection so as to form an exposed portion on the surface, (b) forming a sealing resin on the surface so that the sealing resin is bonded to the exposed portion, and (c) cutting the semiconductor substrate and the sealing resin together along predetermined cutting lines so as to obtain individual semiconductor devices.
According to the above-described method, the portion of the contaminant film is removed by the laser beam projection to form the exposed portion. Therefore, stress generated in the semiconductor substrate when the contaminant film is removed can be reduced compared with a mechanical method in which the contaminant film is removed by machining. Further, the sealing resin is formed to be bonded to the exposed portion so that the bonding strength of the semiconductor substrate and the sealing resin is increased in the exposed portion.
The above objects of the present invention are also achieved by a semiconductor device including a semiconductor chip including external terminals formed on a surface thereof and a sealing resin formed on the surface and sides of the semiconductor chip, wherein a contaminant film formed on the surface of said semiconductor chip has a laser-processed edge so that a peripheral portion of the surface of said semiconductor chip is bonded to the sealing resin.
According to the above-described semiconductor device, the sealing resin is formed on the sides of the semiconductor chip in addition to the surface thereof. Since the contaminant film does not exist on the sides of the semiconductor chip, the bonding strength of the sealing resin and the semiconductor chip is further strengthened.
The above objects of the present invention are also achieved by a method of producing a semiconductor device, which method includes the steps of (a) removing a contaminant from a first surface of a semiconductor substrate by a laser beam projection so as to form an exposed portion on the first surface, and (b) forming groove portions in, the respective linear portions.
According to the above-described method, the contaminant film is removed by the laser beam projection to the exposed portion. Therefore, stress generated in the semiconductor substrate when the contaminant film is removed can be reduced compared with a mechanical method in which the contaminant film is removed by machining.
The above objects of the present invention are also achieved by a method of producing a semiconductor device, which method includes the steps of (a) removing a contaminant from a first surface of a semiconductor substrate by a laser beam projection so as to form an exposed portion on the first surface, (b) forming first groove portions in the exposed portion, (c) forming a sealing resin on the first surface so that the sealing resin is bonded to the exposed portion and the first groove portions, (d) forming second groove portions in the sealing resin and the semiconductor substrate along predetermined cutting lines in the exposed portion by a laser beam projection, and (e) grinding a second surface of the semiconductor substrate with a tape material being applied on the first surface until the second surface is connected with the second groove portions so that the semiconductor substrate is cut along the cutting lines into individual semiconductor devices, the second surface opposing the first surface.
According to the above-described method, the second surface of the semiconductor substrate is ground until the second surface is connected with the second groove portions so that the wafer is cut into the individual semiconductor devices. Therefore, this method does not require a separate cutting process, thus simplifying the production facilities and process. Further, the sealing resin is formed to be bonded to the exposed portion and the groove portions so that the bonding strength of the semiconductor substrate and the sealing resin is increased in the exposed portion and the groove portions.
Moreover, the back grinding process is performed on the semiconductor substrate so that the semiconductor substrate becomes thinner to be prevented from having a warp. During the back grinding process, which is a mechanical operation, great stress is generated in the semiconductor substrate. However, since the exposed portion and the sealing resin are bonded with a high bonding strength, the sealing resin is prevented from coming off the semiconductor substrate even if the stress is applied to the junction of the exposed portion and the sealing resin.
The above objects of the present invention are also achieved by a semiconductor chip included, in a semiconductor device including a sealing resin, which semiconductor chip includes electrode portions formed on a surface thereof and an exposed portion formed on a peripheral portion of the surface, wherein a contaminant film formed on the surface of the semiconductor chip has a laser-processed edge so as to form the exposed portion.
According to the above-described semiconductor chip, the peripheral portion of the contaminant film is removed by the laser beam projection to form the exposed portion on the surface of the semiconductor chip. Therefore, when the semiconductor chip is included in the semiconductor device, the bonding strength of the sealing resin and the exposed portion is increased so as to prevent the sealing resin from coming off the semiconductor chip. Further, since the contaminant film is removed by the laser processing, stress generated in the semiconductor chip when the exposed portion is formed can be reduced compared with a semiconductor chip formed by a method employing a mechanical operation to remove the contaminant. Therefore, even if force resulting from a difference in thermal expansion between the sealing resin and the semiconductor chip is applied to the exposed portion when the semiconductor chip is included in the semiconductor device, the position where the exposed portion is formed is prevented from having a crack or breakage.
The above objects of the present invention are also achieved by a method of producing a semiconductor chip included in a semiconductor device including a sealing resin, which method includes the steps of (a) removing a portion of a contaminant from a surface of a semiconductor substrate by a laser beam projection so as to form an exposed portion on the surface and (b) cutting the semiconductor substrate along predetermined cutting lines so as to obtain individual semiconductor chips.
According to the above-describe method, the portion of the contaminant film is removed by the laser beam projection to form the exposed portion. Therefore, stress generated in the semiconductor substrate when the contaminant film is removed can be reduced compared with a mechanical method in which the contaminant film is removed by machining.
The above objects of the present invention are further achieved by a method of producing a semiconductor chip included in a semiconductor device including a sealing resin, which method includes the steps of (a) projecting a laser beam on a first surface of a semiconductor substrate so as to successively form groove portions in the first, surface along predetermined cutting lines and an exposed portion on the first surface by removing a contaminant film from surroundings of the cutting lines and (b) grinding a second surface of the semiconductor substrate with a tape material being applied on the first surface until the second surface is connected with the groove portions so that the semiconductor substrate is cut along the cutting lines into individual semiconductor chips, the second surface opposing the first surface.
According to the above-described method, the laser beam is projected on the first surface of the semiconductor substrate so as to successively form the groove portions in the first surface along the predetermined cutting lines and the exposed portion on the first surface by removing the contaminant film from the surroundings of the cutting lines. Therefore, the production process can be simplified.
Further, the second surface of the semiconductor substrate is ground until the second surface is connected with the groove portions so that the wafer is cut into the individual semiconductor devices. Therefore, this method does not require a separate cutting process, thus simplifying the production facilities and process. Moreover, the semiconductor substrate becomes thinner by the back grounding so as to be prevented from having a warp.